1. Technical Field
The present invention relates to a liquid jet apparatus, such as an inkjet printer, and more particularly to a liquid jet apparatus whose ejection of liquid droplets is controllable by using a plurality of driving signals.
2. Related Art
A liquid jet apparatus includes a liquid jet head capable of ejecting liquid droplets. The apparatus ejects various types of liquid through the head. Typical examples of such a liquid jet apparatus include an inkjet recording apparatus (printer) having an inkjet recording head (hereinafter referred to as the “recording head”) that ejects droplets of liquid ink, as well as other types of image recording apparatus. In addition, display manufacturing apparatus and various other types of apparatus in which the above-mentioned feature is applied have been available in recent years.
The recording head as an example of the liquid jet head is provided with a continuous ink canal from a common ink (liquid) chamber to nozzles via a pressure chamber. By actuating pressure-generating elements, such as piezoelectric oscillating elements, to change pressure on the liquid in the pressure chamber, the recording head ejects droplets of the ink contained in the pressure chamber. For example, the recording head includes actuator units (oscillator unit) each having a piezoelectric-oscillating-element group joined to a fixing plate, resin head cases each having an accommodation chamber provided for each actuator unit to accommodate the unit, and a canal unit that defines the ink canal.
The canal unit includes, for example, a nozzle plate having a plurality of nozzle openings in row, a canal-forming substrate having a canal base to serve as an ink canal for the pressure chamber, and a sealing plate (oscillating plate) to seal the opening of the canal base in the substrate. The unit has a multilayer structure in which these elements are stacked on top of each other and unified. The sealing plate is made of a compound plate material formed by, for example, laminating a resin film on a stainless steel supporting plate and partly removing the supporting plate. An area on the sealing plate corresponding to the pressure chamber has a diaphragm part that changes the volume of the chamber. The diaphragm part is formed by etching and circularly removing parts of the supporting plate around an area (insular portion) joining the tip of each piezoelectric oscillating element to leave the resin film only.
A free end of each piezoelectric oscillating element in each actuator unit is exposed to the outside of the case through the opening of the accommodation chamber of the case on the canal unit side. The tip of the free end is joined to the insular portion included in the diaphragm part of the sealing plate. By changing the shape of the diaphragm part of the sealing plate with the piezoelectric oscillating element stretching, the volume of the pressure chamber can be increased or decreased. The fixing plate of the actuator unit is made of a stainless steel plate member, for example, and is bonded to an inner wall surface of the accommodation chamber of the case. JP-A-2004-203060 (FIG. 8) is an example of related art.
To miniaturize such a recording head to have a lightweight and space-economical structure, the case and a partition wall defining adjacent accommodation chambers in the case are required to be thinner. Consequently, for example, when one of the actuator units each accommodated in one accommodation chamber is driven to eject ink droplets, the stress generated as a result of a change in the shape of the resin film by the movement of the diaphragm part of the sealing plate may possibly be transmitted to the partition wall, thereby vibrating the wall. If the vibration of the wall is transmitted to the diaphragm part in the other actuator unit, the ejection rate of ink droplets ejected by the driving of this actuator unit may be lowered depending on the phase of the vibration. As the ejection rate of ink droplets ejected is lowered, the airborne droplets may become mist, so that they cannot reach a subject (e.g. recording paper) onto which the ink is ejected. Also, the droplets may not be ejected straight, so that they cannot reach the expected position. These phenomena will degrade the quality of recorded images.